The innumerable shipwrecks dotting the shores of the British Isles over the centuries suggest that GPS navigation might be a bit more foolproof than those methods.

They still are taught (certainly to military navigators), but these techniques are only useful for relatively coarse navigation. Fine to get your boat home to port, but not very useful to accurately locate a particular crab pot, trawl a particular area while avoiding no-go zones or known obstructions, hold station over an dive site, oil or gas well head etc.

Not at all. The effect jamming has on GPS is already well established and can be reliably reproduced in a lab/classroom environment - the receivers mostly just cease to work. Also nothing screams "I am exactly right here" quite like a jammer does, any half decent rack of ELINT gear will locate it within a very short space of time.

The parent is correct.

Did you see his sig?

This is why:

http://en.wikipedia.org/wiki/Global_Positioning_System [wikipedia.org]

After Korean Air Lines Flight 007, carrying 269 people, was shot down in 1983 after straying into the USSR's prohibited airspace,[10] in the vicinity of Sakhalin and Moneron Islands, President Ronald Reagan issued a directive making GPS freely available for civilian use, once it was sufficiently developed, as a common good.[11] The first satellite was launched in 1989, and the 24th satellite was launched in 1994.

Initially, the highest quality signal was reserved for military use, and the signal available for civilian use was intentionally degraded ("Selective Availability", SA). This changed with President Bill Clinton ordering Selective Availability to be turned off at midnight May 1, 2000, improving the precision of civilian GPS from 100 meters (about 300 feet) to 20 meters (about 65 feet). The executive order signed in 1996 to turn off Selective Availability in 2000 was proposed by the US Secretary of Defense, William Perry, because of the widespread growth of differential GPS services to improve civilian accuracy and eliminate the US military advantage. Moreover, the US military was actively developing technologies to deny GPS service to potential adversaries on a regional basis.[12]

GPS is owned and operated by the United States Government as a national resource. Department of Defense (USDOD) is the steward of GPS. Interagency GPS Executive Board (IGEB) oversaw GPS policy matters from 1996 to 2004. After that the National Space-Based Positioning, Navigation and Timing Executive Committee was established by presidential directive in 2004 to advise and coordinate federal departments and agencies on matters concerning the GPS and related systems. The executive committee is chaired jointly by the deputy secretaries of defense and transportation. Its membership includes equivalent-level officials from the departments of state, commerce, and homeland security, the joint chiefs of staff, and NASA. Components of the executive office of the president participate as observers to the executive committee, and the FCC chairman participates as a liaison.

USDOD is required by law to "maintain a Standard Positioning Service (as defined in the federal radio navigation plan and the standard positioning service signal specification) that will be available on a continuous, worldwide basis," and "develop measures to prevent hostile use of GPS and its augmentations without unduly disrupting or degrading civilian uses."

What a load of rubbish.

Near-fleet GPS jamming has nothing to do with ship navigation. Navies have been navigating ships without GPS for several hundred years. GPS jamming is to decoy incoming missiles which use GPS as ONE OF the methods of target location.

Civilians, on the other hand have no critical dependency on GPS. Its largely a toy for the day to day user and a convenient (but non critical) aid for the traveler.

The GPS bands are no where near satellite TV bands.

GPS satellites broadcast at the same two frequencies, 1.57542 GHz (L1 signal) and 1.2276 GHz (L2 signal).
Satellite TV uses the C-band frequencies of 5.4 GHz band (5.15 to 5.35 GHz, or 5.47 to 5.725 GHz, or 5.725 to 5.875 GHz, depending on the region of the world).

Therefore it seems highly unlikely GPS jamming is the cause of any significant TV reception problems.
G-Band (aka C-Band Radar) sits right in the middle of the Satellite TV band, and that is the likely source of any TV interference.

>the ocean is big

Sigh. Mercator Projection [wikimedia.org].

The "ocean" around Scotland is NOT big. The SEA around Scotland is actually quite small. It's as far north as Newfoundland and Labrador.

It just LOOKS big on the map due to two-dimensional maps stretching out the northern and southern extremities of Earth.

Scotland, in particular Faslane, is where NATO keeps its nuclear submarines. The locals live cheek-by-jowl with these submariners and for the most part get along just fine. But closing off all the sea between all the inhabited islands in the west of Scotland just isn't feasible.

>What the hell is a fishing boat doing within 20 miles of a major exercise?

Scotland is only 200 miles x 150 miles in size. A fourty-mile exclusion zone (20 miles radius) would kill the entire marine economy for the western coast of the country.

And the marine economy is pretty much the only economy in western Scotland.